unquoted period in display-name in address field?

[Greg Minshall]

hi.  sorry if this is somewhere faq'd.

i think in RFC822, a period (".") was a "special" so, if included in the
"display-name" part of an e-mail address, would need to be quoted (as
in, 'display.name <display.name@example.com>'.

i occasionally get e-mail messages to which i can't just reply, because
i get an error
----
post: no at-sign after local-part (<) gre.minshall <minshall@umich.edu>: 
Success, continuing...
post: no addressees
send: message not delivered to anyone
----

today, i looked at the newer rfc5322.  if i'm reading it correctly, it
appears that the term "obs-phrase" (which is produced by "phrase', if
i'm using "produced" in the right sense; phrase is produced by
display-name), "suddenly" (well, at least since rfc2822, circa 2020)
allows unquoted periods.

if that's the case.  is post then not obeying the spec?  or, am i
configuring something incorrectly?

cheers, Greg